Specialization of the motor system in infancy: from broad tuning to selectively specialized purposeful actions

In executing purposeful actions, adults select sufficient and necessary limbs. But infants often move goal‐irrelevant limbs, suggesting a developmental process of motor specialization. Two experiments with 9‐ and 12‐month‐olds revealed gradual decreases in extraneous movements in non‐acting limbs during unimanual actions. In Experiment 1, 9‐month‐olds produced more extraneous movements in the non‐acting hand/arm and feet/legs than 12‐month‐olds. In Experiment 2, analysis of the spatiotemporal dynamics of infants’ movements revealed developmental declines in the spatiotemporal coupling of movements between acting and non‐acting arms. We also showed that the degree of specialization in infants’ unimanual actions is associated with individual differences in motor experience and visual attention, indicating the experience‐dependent and broad functional nature of these developmental changes. Our study provides important new insights into motor development: as in cognitive domains, motor behaviours are initially broadly tuned to their goal, becoming progressively specialized during the first year of life.     

“We have no quarrel with you”: Effects of group status on characterizations of “conflict” with an outgroup

In three studies, we examined the effect of intergroup status on group members' tendencies to characterize the ingroup's relationship with an outgroup as conflictual following outgroup action. Findings from all three studies supported the prediction that the intergroup relationship would be characterized as less conflictual when the ingroup had relatively high rather than low status. Consistent with the hypothesis that the effect of status reflects strategic concerns, it was moderated by the perceived relevance of the outgroup's action to intergroup status relations (study 1), it was sensitive to audience (study 2), and it was partially mediated by status management concerns (study 3). The role of strategic, status‐related factors in intergroup relations is discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

QMPE: Estimating Lognormal, Wald, and Weibull RT distributions with a parameter-dependent lower bound

We describe and test quantile maximum probability estimator (QMPE), an open-source ANSI Fortran 90 program for response time distribution estimation.¹ QMPE enables users to estimate parameters for the ex-Gaussian and Gumbel (1958) distributions, along with three “shifted” distributions (i.e., distributions with a parameter-dependent lower bound): the Lognormal, Wald, and Weibull distributions. Estimation can be performed using either the standard continuous maximum likelihood (CML) method or quantile maximum probability (QMP; Heathcote & Brown, in press). We review the properties of each distribution and the theoretical evidence showing that CML estimates fail for some cases with shifted distributions, whereas QMP estimates do not. In cases in which CML does not fail, a Monte Carlo investigation showed that QMP estimates were usually as good, and in some cases better, than CML estimates. However, the Monte Carlo study also uncovered problems that can occur with both CML and QMP estimates, particularly when samples are small and skew is low, highlighting the difficulties of estimating distributions with parameter-dependent lower bounds.     

Combining Trait Models of Impulsivity to Improve Explanation of Substance Use Behaviour

The UPPS‐P model of impulsivity is gaining popularity among personality and substance use researchers, but questions remain as to whether its five facets have incremental validity in explaining substance use over a more parsimonious model specifying only two facets: reward drive and rash impulsiveness. In three cross‐sectional studies (total N = 486), we investigated whether the novel components of the UPPS‐P model (negative Urgency, Premeditation, Perseverance, Sensation seeking, Positive urgency) predicted typical and problematic alcohol and cannabis use after accounting for reward drive, rash impulsiveness and trait neuroticism (assessed with the Eysenck Personality Questionnaire). Reward drive and rash impulsiveness scores were calculated using principal components analysis of multiple scales, including UPPS‐P premeditation and sensation seeking. Results showed that rash impulsiveness was a robust predictor of typical and problematic substance use. The novel facets of the UPPS‐P did not improve prediction of typical substance use. The urgency scales inconsistently predicted problematic use. Specifically, negative urgency predicted one of three measures of negative consequences from alcohol use, and positive urgency only predicted negative consequences from cannabis use. Results suggest that the three novel facets of the UPPS‐P model add little over a two component model in explaining substance use, although may provide preliminary evidence for the utility of a revised global urgency construct in explaining problematic substance use. Copyright © 2017 European Association of Personality Psychology     

Task Decomposition Through Competition in a Modular Connectionist Architecture: The What and Where Vision Tasks

A novel modular connectionist architecture is presented in which the networks composing the architecture compete to learn the training patterns. An outcome of the competition is that different networks learn different training patterns and, thus, learn to compute different functions. The architecture performs task decomposition in the sense that it learns to partition a task into two or more functionally independent tasks and allocates distinct networks to learn each task. In addition, the architecture tends to allocate to each task the network whose topology is most appropriate to that task. The architecture's performance on “what” and “where” vision tasks is presented and compared with the performance of two multilayer networks. Finally, it is noted that function decomposition is an underconstrained problem, and, thus, different modular architectures may decompose a function in different ways. A desirable decomposition can be achieved if the architecture is suitably restricted in the types of functions that it can compute. Finding appropriate restrictions is possible through the application of domain knowledge. A strength of the modular architecture is that its structure is well suited for incorporating domain knowledge.     

Repetition Priming Follows Spontaneous but not Prompted Recognition of Familiar Faces

Reaction times to make a familiarity decision to the faces of famous people were measured after recognition of the faces in a pre-training phase had occurred spontaneously or following prompting with a name or other cue. At test, reaction times to familiar faces that had been recognized spontaneously in the pre-training phase were significantly facilitated relative to an unprimed comparison condition. Reaction times to familiar faces recognized only after prompting in the pre-training phase were not significantly facilitated. This was demonstrated both when a name prompt was used (Experiments 1 and 3) and when subjects were cued with brief semantic information (Experiment 2).

Repetition priming was not found to depend on prior spontaneous recognition per se. In Experiment 3, spontaneously recognizing a familiar face did not prime subsequent familiarity judgements when the same face had only been identified following prompting on a prior encounter. In Experiment 4, recognition memory for faces recognized after cueing was found to be over 90% accurate. This indicates that prompted recognition does not yield repetition priming, even though subjects can remember the faces. A fusion of “face recognition unit” and “episodic record” accounts of the repetition priming effect may be more useful than either theory alone in explaining these results.     

Elemental and Configural Processes in Patterning Discrimination Learning

Three experiments used appetitive conditioning with rats to examine the involvement of elemental and configural processes in positive and negative patterning discriminations. The first experiment demonstrated that negative and, to some extent, positive patterning discriminations were learned more rapidly when these discriminations consisted of stimulus elements that had previously been the reinforced as opposed to the non-reinforced elements of a simple discrimination. Experiment 2 revealed an excitatory summation effect during the early phase of negative patterning learning that depended upon discrimination pretraining. The final experiment demonstrated faster discrimination learning between the compound and the less salient, rather than the more salient, element of an instrumental patterning task. The present set of results were interpreted as reflecting the possibility, consistent with connectionist theory, that internal representations of the conditioned stimuli change over the course of a patterning discrimination.     

The effects of post-encoding stress on recognition memory: examining the impact of skydiving in young men and women

Prior studies have indicated that post-encoding stress can protect memories from the effects of forgetting, and this has been taken as evidence that stress facilitates memory consolidation. However, it is not known whether stress acts by directly influencing the strength of the underlying memories or whether it influences the generation process that plays a critical role in tests such as free recall. To address this issue, we examined the effects of stress produced by skydiving on recognition memory for negative and neutral pictures. Relative to a non-stress control condition, post-encoding stress in males was found to increase recognition memory for neutral pictures. However, stress was not found to improve recognition for emotional pictures, nor was it found to influence recognition memory in female participants. Additional analysis of recognition performance suggested that stress increased familiarity-based recognition rather than recollection. This study indicates that stress can improve familiarity-based recognition, thus showing that stress directly increases the strength of the underlying memories.